This invention relates to paperboard cartons designed primarily for use in the fast food industry, although they may be readily used to package other items. Cartons manufactured for this service are sold in vast numbers to dispense hamburgers, sandwiches and other hot and cold foods. These cartons must possess a number of basic features. They must be nestable in the open position to reduce bulk while waiting to be put into service. They must possess the requisite strength to resist distortion due to the rapid handling motion of the server in taking an open carton, filling it with a food item, closing it to a locked position, and then serving it to a customer. They also must be capable of being reopened and reclosed without damage. This latter feature is important in the event the customer belatedly requests some special service.
In addition to the above, cost plays an important role. The paperboard must be of the highest quality to be used for food service. The material is quite expensive and requires the carton to be designed to yield minimum scrap when stamping the blank forming the carton. Many carton designs, while meeting the basic features discussed above, are so wasteful of paperboard as to be economically noncompetitive.
A large number of foldable paperboard cartons have been invented, as typified by U.S. Pat. Nos. 4,570,845, issued Feb. 18, 1986, to Charles J. Hall; 4,232,816, issued Nov. 11, 1980 to Fred J. Johnson et al; and 2,544,565, issued Mar. 6, 1951 to Lawrence H. Phillips.
The patent to Hall shows a foldable paperboard carton having laterally extending locking tabs in the cover which are inserted in slots provided in the tray side panels. To engage or disengage the lock, the cover must be laterally deformed to pull the tabs away from the slots. Johnson et al show a foldable paperboard carton having a single tab mounted on the front panel of the cover. This tab locks into a single latching slot mounted in the upper portion of the tray front wall. Phillips shows a foldable paperboard carton with forwardly directed tabs on a lower portion of the front panel of the tray. The cover has slots which lock onto the tabs in the closed position.
While the above representative patents do teach foldable paperboard cartons with reusable front locks, the prior art does not teach a carton design of sturdy construction with minimal waste of material such as found in this invention.